1. Field of Invention
Wood of the genus Juglans which is jet black completely and throughout its entire structure and substance, thereby providing an ebony substitute, and method of producing the same.
2. Prior Art
There is a dwindling availability of natural ebony. Diospyros ebenum, or Ceylon Ebony, which is considered to be the finest and blackest variety, is virtually unobtainable in lumber form and is available on a limited basis in small dimension stock only. Diospyros spp., or Nigerian Ebony, the most commonly used black ebony, is available only in small boards which generally contain numerous defects. The supply of this wood is unreliable and its quality is generally poor (7). The cost of natural ebony is very high, being about eight times the price of walnut, an available domestic wood which can conveniently be employed as starting material for the present invention.
Natural ebony has been a rare, expensive, and highly-prized wood since ancient times. There has never been a sufficient supply available to enable its extensive use in furniture construction or other large works. Most uses of ebony have therefore been for such purposes as decorative inlay work, small accessory furnishings, musical instrument parts, fancy handles, piano keys, and the like (2, 4).
Although problems of supply, quality, and cost preclude the use of ebony in furniture and many other products, the popularity of, and demand for, "ebony colored" wood and wood substitutes has been, and continues to be, very strong. This is evident from many examples seen in furniture, accessory furnishings, musical instruments, sporting goods items, cutlery, and other products. The term "ebonized finish" is often used in reference to the finishes on these items.
The demand for ebony color is met in various ways including surface coloring of white woods by painting or staining them black, the use of black plastics, and the use of white woods impregnated with black dyes, black dye/resin combinations, or chemicals. None of these methods provides a satisfactory ebony substitute and all have various shortcomings. Painted surfaces do not look like wood. Stained wood falls short of the quality of appearance which is obtained in wood which is finished in its natural color without the use of stains. Both finishes are easily abraded or damaged, revealing the underlying white wood. Plastics are unsatisfactory substitutes.
Several methods have been devised over the years to color-impregnate wood with various colors, including black. These methods fall into the following general classifications: dye impregnation, dye/resin impregnation, dye/resin impregnation and compression of wood, and chemical impregnation. In the areas of dye impregnated and dye/resin impregnated woods, when black colors are produced, they lack the intensity of the black color of natural ebony (3). It has also proven impossible to completely impregnate woods with these substances (8). There always remain certain areas in the wood which are impervious to the dyes or dye/resin combinations. This results in unattractive colored streaks being visible in the finished material. Ray cells are particularly impervious to dyes and areas of ray fleck figure are present in much of the wood which remains undyed. In an effort to overcome these difficulties, methods have been developed to dye thin sheets of wood veneer, these being more readily impregnated than lumber (8), and then to laminate the veneer sheets into stock of the desired thickness. This material is in common use in the archery industry for bow handles (9), but still fails to overcome the previously-noted shortcomings of dye-impregnated woods. In addition, it has the objectionable characteristic of looking like plywood, which is what it is. This material is suitable for certain specialized applications but its use is not widespread, and it most assuredly is not considered to be an ebony substitute.
In the area of dye/resin impregnated and compressed wood, a material generally known as "Compreg", more intense colors than those of previously-described materials are generally achieved. However, the problems associated with dye-impregnated wood, especially unimpregnated areas, remain in this material. In addition, it has the objectionable characteristics of looking like plywood, being extremely hard and heavy, being very brittle, and consisting more of resin than of wood. This material is in common use in the cutlery industry for handle material. However, its use is even more restricted than that of the previously-described laminated material and it is likewise not considered to be an ebony substitute.
The area of chemical impregnation of wood to change its color, as it relates to creating a black color, is discussed further hereinafter. Such processes produce colors with the characteristics of natural wood colors, in that the colors are imparted into the cell structure of the wood and are not laid on the wood surface as are stains. Such woods, when finished, have the same quality of appearance as woods finished in their natural colors without the use of stains. While the foregoing procedure will produce wood materials with gray, or gray-black color, it has proven impossible to duplicate the intense black color of natural ebony with this procedure, for reasons further explained hereinafter.
The desirable characteristics of the finest natural ebony include, in addition to the primary characteristic of its color, susceptibility of polish, hardness, and durability (2,4).
Natural ebony also has certain undesirable characteristics that include excessive hardness, excessive weight, brittleness, difficulty of machining causing it to be hard on cutting tools, excessive degrade due to the numerous defects which it contains, availability in small dimensions only, inadequate and unreliable supply, and excessive cost.
The finest grade of natural ebony is generally considered to be the species Diospyros ebenum, or Ceylon Ebony. This ebony is believed to excel all other varieties in the fineness, uniformity, depth, and intensity of its black color (4). Heretofore it has been impossible to duplicate this color in artificially color-impregnated wood materials.
The prior art, to the extent of my knowledge from studies and searches, is as follows:
(I) Ebonized oak, a process of surface treating oak lumber with an aqueous solution of ferrous acetate (11), in which the iron in the solution reacts with tannin in the oak, forming ferric tannate, a compound of variable composition and of bluish-black color. This imparts a bluish-black or bluish gray color to the wood surface. An aqueous solution of ferrous sulfate can be used in place of ferrous acetate.
(II) Surface treatment of white woods with an aqueous solution of tannic acid, followed by a surface treatment with an aqueous solution of ferrous sulfate. This process likewise forms ferric tannate and imparts a gray to gray-brown to gray-black color to the wood surface.
(III) Impregnation of white woods with aqueous solutions of tannic acid and iron salts (1,13). This process forms tannic acid on the wood surface and on its interior portions. It imparts colors ranging from gray to gray-black to black. However, this process will not impart a black color with the deep intensity of the black color of natural ebony. The reasons for this are not understood, but may have to do with the fact that a given volume of wood has a very large surface area within it due to its microscopic cellular structure, and it may not be possible to introduce enough tannic acid to effectively cover this surface area. In numerous experiments which I have conducted on permeable woods, which are most readily impregnated, using the tannic acid-iron salt solution process, I have been unable to achieve an intense black color using prior art procedure.
The art of impregnating wood is well known and widely practiced in industry. However, the complete impregnation of the entire structure and substance of woods is neither known nor practiced. It is of course not necessary or desirable in the wood preservation industry (12). It is not achieved in dye or dye-resin impregnated wood, as evidenced by the uncolored, unimpregnated areas which still remain in these products.
Due to the shortcomings of all of these available procedures, the art has taken to dye and dye-resin impregnated woods but here, as previously stated, the intense black color of ebony has not been duplicated to date (3) and, moreover, complete impregnation of woods with such substances has proven impossible (8).
Additional comments concerning patents turned up in a patent search relating to the subject of this invention are as follows:
Spicker, U.S. Pat. No. 3,635, 1844, discloses and claims an "Improved Method For Coloring Wood". The method there described does not provide complete coloring throughout the structure of the wood, cannot be employed to produce a totally black product, even using thin pieces of veneer, does not provide an economic or commercially feasible process, does not specify the species of wood to be employed, can only produce pastel or medium color shades and certainly cannot be employed to produce an ebony substitute.
Spade, British Patent No. 152,427, 1920, discloses and claims impregnation of wood with tannin, followed by iron salt, then necessarily supplemented with a dye. claims production of a wood product which is uniformly black throughout. Requires the employment of ammonia and thereafter a logwood extract and cannot be used to produce a totally black wood product suitable as an ebony substitute. It also discloses use of ferrous acetate after capeachy extract plus soap solution, which also cannot be used to produce a wood which is sufficiently black throughout to be employed as an ebony substitute.
Lentz, U.S. Pat. No. 1,809,980, 1931, discloses the employment of ammonia gas to color a white wood a brown or walnut color, thereby producing a walnut substitute. U.S. Pat. No. 929,015 roughly covered the same idea in 1909.
Black, U.S. Pat. No. 2,391,613, 1945, discloses the dyeing of wood by impregnation with an azo pigment and forming the pigment within the wood structure.
Hill, U.S. Pat. No. 3,695,920, 1972, describes the surface coloring of wood with pigments prior to using the wood for impregnation with wood-preservative chemicals.
Hyatt, U.S. Pat. No. 209,568, 1878, discloses a surface treatment of wood with tannin derived from logwood extract followed by a treatment with tincture of muriate of iron or use of the same two substances together as a stain. This patent applies a basic idea which predated the patent by many, many years.
Hall, U.S. Pat. No. 939,015, 1909, discloses impregnation of white wood with ammonia gas to impart an oak appearance to white wood and uses heat and vacuum to extract air and moisture from thewwood being treated. This patent discloses the same idea as U.S. Pat. No. 1,809,980, approximately twenty-two years later.
Hall, U.S. Pat. No. 964,017, 1910, discloses the impregnation of white wood with metallic salts so that the salts react with the tannin found naturally in the wood to produce a "light" shade of color different from the natural wood and produce a ring-developed or figured effect in woods in which the "grain is comparatively inconspicuous". Silver grays and light browns are the colors of the ultimate product.
Farber, U.S. Pat. No. 2,517,296, 1950, discloses a method of changing walnut sapwood, which is white, to a color closely resembling the walnut heartwood, which is brown, by immersing the wood in an aqueous solution of hydroquinone for two to sixty hours and thereafter exposing the wood to ammonia vapor.
Mengel, U.S. Pat. No. 1,774,940, 1930, discloses a method of changing the color of walnut sap veneer, which is white, to the color of walnut heartwood, which is brown, by soaking the veneer in a solution of tannic acid and iron salt thereby to turn the color of the walnut sapwood into the color of the walnut heartwood. The treated veneer is only 1/28th inch thick.
Hall, U.S. Pat. No. 924,770, 1909, discloses the impregnation of white wood with a dye which is made from phlobaphenes of hemlock or oak bark, which are byproducts in the production of extracts for the tanning industry. The colors achieved are various shades of brown.
Dunn, U.S. Pat. No. 3,685,959, 1972, discloses the impregnation of wood with halogenated hydrocarbon solvents or polyethylene glycol plus desired preservatives and dyes, fire retardants, and what have you.
Simatupang, DE No. 3,344,973, published in 1985, discloses a surface wood stain comprising tannin, a ferrous salt, an ammonium salt, and a water-soluble polyhydric alcohol.
Bouwman, U.S. Pat. No. 1,447,528, on an application filed in 1922, discloses a method of fixing dyes into wood which has been impregnated with an aqueous dye solution which makes it possible to compress the wood without driving out the dye.
Hall, U.S. Pat. No. 939,016, 1909, discloses a method of color-impregnating wood with dyes in which the step of steaming or boiling is employed.
Nack, U.S. Pat. No. 2,867,493, 1959, discloses a process of pretreating a wood surface so that subsequent dye application causes reaction with the chemical left from the first pretreatment step, resulting in a surface-stained wood.
Williams, U.S. Pat. No. 3,622,380, 1971, discloses a method of coloring white wood a walnut color involving employment of furfuryl alcohol, a metallic compound acting as catalyst, and a complexing agent such as lactic acid or ammonium chloride. The claimed color impregnation is effected by soaking one inch by one inch samples of veneer in the solution.
From the foregoing, it is clear that the prior art has not provided any suitable or satisfactory ebony substitute, whether highlighted or essentially devoid of highlighting, or any method of producing the same, much less such a method which is economically and commercially feasible, generally applicable to large wood sizes, equivalent throughout its composition and substance to ebony in its degree of jet black color, darkness, depth, and intensity, which is stable and with no tendency for color bleed-out or fading. It also is apparent that the expense and relative unavailability of natural jet black ebony, despite the efforts of the prior art and in view of the obvious shortcomings of the prior art, now places a suitable and satisfactory jet black ebony substitute, such as is provided by the present invention, and an economic and commercially-feasible process for the production thereof, into the category of a "long-awaited" development, especially since efforts to produce satisfactory ebony substitutes have continuously been made over a period of at least 100 years without any substantial measure of success.